Refrigeration



May 5, 1942! M- E- BIXLER ETAL 2,281,823

' REFRIGERATION I Filed Oct. 10, 1938 2 Shee ts-Sheet 1 INVENTORS Milo E Bixler Curtis 6. 600.126

ATTOR N EY May 5, 1942'v M. E. BIXLER ETAL REFRILGERATION Filed Oct. 10, 1938 Milan? 5:15:5 1'? Curtis C. 60022:;

2 Sheets-Sheet 2 l Patented May 5, 1942 UNITED STATES PATENT OFFICE REFRIGERATION Application October 10, 1938, Serial No. 234,166

Claims.

This invention relates to the art of absorption refrigeration and more particularly to an improved evaporator construction for use therewith.

In the copending application of Curtis C. Coons and William H. Kitto, filed April 2, 1941, Serial No. 386,395, which is a continuation-inpart of their application filed July 20, 1938, Serial No. 220,189, there is disclosed an absorption refrigerating system including an evaporator in which the liquid refrigerant and inert gas are supplied to the bottom portion of the evaporator and circulate upwardly therethrough as the liquid refrigerant evaporates into the inert gas to produce useful refrigeration. This evaporator construction is functionally satisfactory but it possesses the disadvantage that it cannot be heightened sufficiently to accommodate a double depth ice cube tray and two single depth ice cube trays vertically positioned without increasing the pressure drop between the gas inlet and outlet portions thereof. It is undesirable to increase the pressure drop between the gas inlet and outlet portions of the evaporator because this necese sitates increasing the size of the circulating'fan which in turn increases the necessary depth of the mechanism compartment at the rear of the refrigerator cabinet. According to the present invention there is provided an evaporator structure in which the evaporator may be made of sufficient height to accommodate a double-depth ice cube tray and two single depth ice cube trays without increasing the pressure drop between the gas inlet and outlet portions of the evaporator characteristic of previous constructions.

It is a further object of the present invention to provide an evaporator structure of the above described type in which the liquid refrigerant is lifted from the lowest point to an intermediate portion of the evaporator in a single stage and in which the liquid refrigerant is elevated a greater distance from an intermediate portion of the evaporator to an upper portion thereof through a plurality of stages.

It is a further object of the invention to provide an evaporator of the type involving a plurality of horizontal coil sections connected by riser elements in which the riser elements areturned inwardly into the plane of a wall of the evaporator thereby to conserve space and to improve the cooling efficiency of the evaporator as a whole.

It is a further object of the invention to provide an evaporator of the type in which the liquid refrigerant is circulated through the evaporator by the impetus imparted thereto by a propelled stream of pressure equalizing medium in which the pressure equalizing medium is enabled to elevate the liquid through a greater distance than that possible with previous constructions with substantially the same pressure drop in the gas stream.

Other objects and advantages of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawings, in which:

Figure l is a diagrammatic representation of a refrigerating system embodying the invention in which certain portions are shown on an enlarged scale and in perspective.

Figure 2 is a diagrammatic perspective view of a modified form of evaporator construction.

Referring now to Figure 1 in detail, there is disclosed a continuous absorption refrigerating system of the three-fluid type embodying a boiler B, an analyzer D, a rectifier R, a condenser C, an evaporator E, a gas heat exchangerG, a liquid heat exchanger L, an absorber A, a solution reservoir S, and a circulating fan F which is driven by an electrical motor M. These elements are suitably connected together by various conduits to form a plurality of gas and liquid circuits, to which reference will be made in more detail hereinafter, constituting a complete refrigerating system.

The above described refrigerating system will be charged in any suitable manner with a refrigerant, such as ammonia, an absorbent, such as water, and an inert pressure equalizing medium, preferably a dense inert gas such as nitrogen.

The boiler B may be heated in any desired manner as by an electrical cartridge heater or by a combustible fuel burner.

The circulating motor M and the heater for the boiler B will also be controlled in any desired manner. A preferred control mechanism is disclosed in the copending application of Curtis C. Coons, Serial No. 148,424, filed June 16, 1937, now Patent No. 2,228,343, issued January 14, 1941.

The application of heat to the boiler B generates refrigerant vapor from the strong solution normally contained therein. The refrigerant vapor so generated passes upwardly through the analyzer D in counterflow to strong solution flowing downwardly therethrough. In the analyzer, vapor of absorption solution generated in the boiler is condensed by contact with the strong solution and the heat of condensation serves to generate further refrigerant vapor which then passes through the conduit II to the upper por tion of a tubular air-cooled condenser C. The conduit H includes the rectifier R which serves to cause condensation of any vapor of absorption solution which may pass through the analyzer D.

The refrigerant vapor discharges into the condenser and flows downwardly therethrough and is condensed by heat exchange with cooling air flowing over the outer surface of the condenser and the fins attached thereto. The condensate formed in the condenser C is drained therefrom through a conduit l2 into the bottom portion of the evaporator E to which reference will be made in more detail hereinafter.

The weak solution formed in the boiler B by the generation of refrigerant vapor is conveyed therefrom through a conduit IS, the inner path of the liquid heat exchanger L and a conduit 16 which discharges into the upper end of the tubular air-cooled absorber A. For purposes of convenience, the absorber A has been shown as being vertically positioned herein. However, it may be positioned in any plane from the vertical to a plane inclined slightly to the horizontal. It is apparent that the upper portion of the absorber is at an elevation above the liquid level normally prevailing in the boiler-analyzer system wherefore some means must be provided to elevate the weak solution thereinto. For this: purpose a small bleed conduit I1 is connected between the gas discharge conduit I8 of the circulating fan F and the weak solution conduit l6 below the liquid level normally prevailing therein, whereby the weak solution is elevated into the absorber by ga lift action. The weak solution flows downwardly through the absorber in counterflow relationship to a rich mixture of pressure equalizing medium and refrigerant vapor which is conveyed thereto in a manner to be described more fully hereinafter. In the absorber the refrigerant vapor content of the mixture is absorbed by the solution which then becomes strong solution and flows to the bottom portion of the absorber where it is drained through a conduit 20 into the strong solution reservoir S. The heat of absorption generated by the absorption process is rejected to air flowing over the outer walls of the absorber vessel and in contact with the air-cooling fins mounted thereon. The strong solution is conveyed from the reservoir S through the conduit 22, the outer path of the liquid heat exchanger L, and the conduit 23 to the upper portion of the analyzer D.

The lean inert gas discharged by the circulating fan F enters the outer path of the gas heat exchanger G from which it is conveyed through the conduit 25 to the bottom portion of the evaporator E. The evaporator E will be described in detail hereinafter. For the present it is sufiicient to state that the propelled stream of inert gas discharging through the conduit 25 circulates upwardly through all portions of the evaporator carrying the liquid refrigerant upwardly therewith as it evaporates into the inert gas stream. The rich mixture formed in the evaporator is discharged therefrom through the conduit 28 into the inner path of the gas heat exchanger Gfrom which it is conveyed through the conduit 29 to the bottom portion of the absorber A. The rich mixture passes upwardly through the absorber A in counterflow relationship to the solution flowing downwardly therethrough by gravity in the manner described herebefore. The lean gas formed in the absorber is conveyed from the upper portion thereof into the suction line of the circulating fan F by a conduit 39, thus completing the inert gas circuit.

The evaporator per se comprises a lower W- shaped coil 33, an intermediate W-shaped coil 34, an upper S-shaped coil 35, and an upper large diameter finned box-cooling conduit 38. The inert gas inlet conduit 25 communicates with one end of the coil section 33, and the liquid refrigerant supply conduit 12 communicates with the conduit 33 adjacent its point of connection with the supply conduit 25. The coil sections 33 and 34 are connected by a vertical riser conduit 39. The coil sections 34 and 35 are connected by a double riser conduit system comprising a riser conduit section 4|, a substantially horizontal conduit section 42 extending across the back portion of the evaporator, and a second riser conduit section 43 which opens into the inlet end of the S-shaped coil section 35. The coil section 35 is connected to the forward end of the conduit 38 by a short riser conduit 44. The large diameter conduit 38 is tilted slightly backwardly from its point of connection with the conduit '44 to its point of connection with the conduit 28 in order to permit the liquid refrigerant to flow therethrough by gravity. A drain .conduit 46 opens into the top portion of .the conduit 33 adjacent its point of connection with the riser conduit 39 and connects to the strong solution return conduit 22. i

It will be understood that the refrigerating system will be encased in a suitable cabinet with the mechanism properly distributed in lower and rear mechanism compartments and with the evaporator projecting into the storage compartment of the cabinet. The evaporator of course will be encased in a suitable housing including shelves resting on the various coil sections 33 and 3G to support ice cube trays.

The evaporator including the conduit 25 :may, if desired, be constructed of a single piece of relatively small diameter tubing, on the order of onehalf inch inside diameter, for example, or .it may be constructed of suitably shaped sections of tubing welded together as may be desired.

The operation of this form of the invention will now be'described. The propelled stream of inert gas discharging through the conduit .25 i travelling at a high velocity as compared with .gas velocities previously used in the evaporators of absorption refrigerating systems and it sweeps or drags the liquid refrigerant supplied from the conduit l2, throughout the evaporator into the box-cooling conduit 38.

The action of the inert .gas on the liquid .refrigerant is as follows: In substantially'horizontal and slightly inclined conduits the gas stream passes over the surface of .asmall stream of the liquid which it propels through the conduit :by the dragging or frictional action exerted on the liquid by the gas. Inrising and steeply inclined conduits the action is somewhat different, the liquid refrigerant collects to some extent and is maintained in a state of continual violent agitation by the continual discharge of inert gas therethrough, which inert gas blows, sweeps o1 drags a portion of the collected liquid into the next higher evaporator conduit where the gas again propels the liquid into a stream as mentioned above.

As explained in the said copending application of Kitto and Coons, the propelling action of the inert gas is a function of its density, pressure, and velocity of flow. It has been shown by experience that it is desirable to 'develop'approximately 4 /2" of water pressure across the circulating fan F for refrigerators adapted to be used in conventional size domestic cabinets. Of this total resistance drop in the inert gas circuit, only between 2 /2" to 3" of Water pressure may be used up between the gas inlet and outlet connections to the evaporator as the remainder of the pressure drop is used up to force the gas to flow through the various conduits,'the gas heat exchanger and the absorber. It has also been found with a system using nitrogen and with a system pressure ranging between 270 and 400 pounds per square inch using evaporator conduits of approximately inside diameter that this pressure drop will circulate the liquid through an evaporator conduit of approximately or 11 in height and arranged to receive a double depth ice tray resting upon the shelf placed above the coil sections 33 and 34; however, it is desirable to stack two single depth ice trays between the coil sections 34 and 35. This necessitates an increase in the evaporator height of a magnitude of /2"-to 1 depending upon the particular design. However, it has been found that a single lift, such as the conduit 39 extend ing between the coil section 3-1 and 35, it is not altogether reliable in operation if the extra height is added between the coils 3 1 and 35 and that continued operation under these conditions can be assured only by increasing the pressure drop of the inert gas across the evaporator, which of course necessitates an increase in the speed or the size of the fan which is undesirable because of the increase in depth of the mechanism compartment at the rear of the refrigerator cabinet. The present invention obviates this difficulty without measurably increasing the pressure drop between the gas inlet and outlet connections of the evaporator by talring the higher lift between the coil sections 34 and 35 in two stages of relatively small extent. The reason that this construction permits a greater lifting height without a measurable increase in' pressure drop appears to be due to the fact that the major portion of the throttling action of the inert gas in the evaporator occurs in the vertical lift portions thereof and that the throttling action increases more rapidly than a straight line function with increasing lifting height. Therefore, by using two small lifts instead of a single lift, the liquid may be elevated through a height greater than that possible with a single lift with the same pressure differential. This is highly advantageous and makes the evaporator construction more flexible in the hands of the designer and, as heretofore noted, permits the utilization of double depth ice trays in the bottom portion of the evaporator and of two single depth ice trays in the upper portion thereof, thus giving the housewife a reasonable choice of tray capacity when ice cubes are in demand.

In Figure 2 there is illustrated a modified form of the invention. The evaporator construction illustrated in this figure is designed and intended to be utilized in exactly the same relationship to the system as the evaporator illustrated in Figure 1. Therefore, a full and complete description of the system is regarded as unnecessary. Certain portions of the evaporator construction illustrated in Figure 2 are identical with portions of the construction illustrated in Figure 1 and are therefore given the same reference characters primed.

The coil sections 33 and 34' of the evaporator of Figure 2 are identical with that of Figure 1 except that the inlet and outlet connections thereof are on opposite sides as will be apparent from a study of the two figures. This has no effect on the functioning of the apparatus. The coil section 33' is connected to the coil section 34 by a riser conduit 60 which as illustrated is turned inward to lie in the plane of the rear wall of the evaporator instead of extending backwardly therefrom as is the case with the riser 39 illustrated in Figure 1. The elevating conduit connecting the evaporator sections 34' and 35 is distinctly different from that utilized in connection with the evaporator in Figure l. The outlet portion of the coil section 34 communicates with a horizontal conduit 6| extending horizontally part way across the back portion of the evaporator in the plane of the rear wall thereof. The conduit 6| communicates with a riser conduit 62 which communicates with a secelusive.

ond horizontal section 63 which extends to the side of the evaporator opposite to the side upon which the ga outlet portion of the coil section 34 terminates and communicates with a second riser section 64 which terminates in a horizantal conduit 65 extending across the rear portion of the evaporator and joining with the gas inlet portion of the S-shaped coil section 35'.

In this form of the invention the entire trans-- ferring mechanism for conveying the liquid refrigerant from the coil sections in one elevation to the coil sections at a, higher elevation are turned inwardly in one way or another into the plane of the rear wall of the evaporator. This includes all those elements numbered to 65, in-

This arrangement appreciably improves the space economy of the evaporator construction for the reason that the riser conduits do not extend backwardly beyond the efiective rear end of the evaporation area as determined by the W and S-shaped coil sections 33, 34' and 35'. Therefore, the evaporator may be made deeper or it may be placed further toward the rear wall of the cabinet and thus occupy less space than the evaporator disclosed in Figure 1 but without altering the efliciency or operation thereof. Additionally, the riser conduit sections 50 to (i5, inclusive, aid the refrigerating effect produced within the evaporator because they are in reasonably intimate heat transfer relationship with the rear wall thereof.

The evaporator disclosed in Figure 2 operates substantially as the evaporator disclosed in Fig ure 1 and produces the same results, the sole difference being the difference in the double riser elevating sections and in the manner in which the elevating conduits turn inwardly into the plane of the rear wall of the evaporator to conserve space.

Accordingly, the present invention provides an evaporator construction permitting maximum height between various portions thereof without adversely affecting the pressure differential be-- tween the gas inlet'and outlet portions thereof. Furthermore, there is provided a liquid circulating device in which the liquid is elevated through a plurality of small steps to a height much greater than would be possible with the same energy expenditure if the liquid were elevated in a single step. These desirable results are accomplished without adversely affecting any other portion of the system or requiring any change in the design thereof and further permit the evaporator construction to occupy a minimum of otherwise useful space within the refrigerator storage compartment.

By permitting the total evaporator height to be increased the designer is given larger latitude in the design of the air-cooled condenser as the height of the condenser may be increased or it. may be placed lower in the rear air cooling flue of the cabinet, in which the condenser is customarily positioned, without altering the cabinet construction, increasing the depth of the cooling air flue or altering the circulating fan. This is highly advantageous because the eificiency and appearance of the finished machine are largely dependent upon the provision of an adequate condenser which does not extend above the top wall of the cabinet.

While the invention has been illustrated and described in detail it is not to be limited thereto but various changes may be made in the construction, design and arrangement of parts without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. Absorption refrigerating apparatus of the type including an evaporator, means for supplying refrigerant liquid to said evaporator, and means for propelling a pressure equalizing medium upwardly through the evaporator under conditions such that the pressure equalizing medium will drag or sweep liquid refrigerant through the evaporator as it travels therethrough, characterized in that said evaporator includes a plurality of sections at different elevations and multistaged lifting conduits interconnecting evaporator sections at adjacent elevations,

2. Absorption refrigerating apparatus comprising an evaporator, means for supplying liquid refrigerant to the lower portion of said evaporator, and means for propelling an inert gas upwardly through said evaporator under conditions such that it will drag or sweep liquid refrigerant therethrough, characterized by the fact that said evaporator includes a plurality of substantially horizontal section interconnected by rising conduits through which the gas and liquid flow, one of said rising conduits comprising a staged lifting arrangement including at least two lifting conduits and at least one "horizontal rest conduit therebetween.

3. Absorption refrigerating apparatus comprising an evaporator, means for supplying liquid refrigerant to the lower portion of said evaporator, and means for propelling an inert gas upwardly through said evaporator under conditions such that it will drag or sweep liquid refrigerant therethrough, characterized by the fact that said evaporator includes a plurality of substantially horizontal sections interconnected by rising conduits through which the gas and liquid flow, one Of said rising conduits comprising a staged lifting arrangement including at least two lifting conduits and at least one horizontal rest conduit therebetween, said staged lift conduit lying substantially within the plane of the rear wall of said evaporator.

4. Absorption refrigerating apparatus comprising an evaporator, means for supplying liquid refrigerant to the lower portion of said evaporator, and means for propelling an inert gas upwardly through said evaporator under conditions such that it will drag 'or sweep liquid refrigerant therethrough, characterized by the fact that said evaporator includes a plurality of substantially horizontal sections interconnected by rising conduits through which the gas and liquid flow, one of saidrising conduits comprising a staged lifting arrangement including at least two lifting conduits and at least one horizontal rest conduit therebetween, said staged lift conduit lying substantially within the plane of the rear wall of said evaporator, and a single stage lift conduit interconnecting other adjacent sections of said evaporator also lying in the plane of the rear wall thereof,

5. Refrigerating apparatus comprising an evaporator, means for supplying liquid refrigerant to the bottom portion of said evaporator, and means for propelling an inert gas through said evaporator under conditions such that it will convey unevaporated refrigerant upwardly therethrough, said apparatus being characterized in that said evaporator comprises a plurality of horizontally positioned vertically spaced coils defining freezing zones therebetween, an elevating conduit communicating an adjacent pair of coils, and a multi-stage elevating conduit system lying in the plane of the rear wall of said evaporator and including at least two riser conduits of less depth than said first mentioned riser conduit connected by a horizontal rest conduit communicating one of the coils of said pair of coils and another vertically spaced coil.

6. An evaporator comprising a pair of vertically spaced W-shaped coil sections, a superposed S-shaped coil section, a riser conduit connecting said W-shaped coil sections, and a riser conduit including a pair of upstanding sections spaced by a substantially horizontal section connecting said S-shaped coil section and the adjacent W-shaped coil section.

7. An evaporator comprising a pair of vertically spaced W-shaped coil sections, a superposed S-shaped coil section, a riser conduit connecting said W-shaped coil sections, a riser conduit including a pair of substantially vertical sections spaced by a substantially horizontal section connecting said S-shaped coil section and the adjacent W-shaped coil section, a large diameter finned conduit positioned above said S-shaped coil, and a riser conduit connecting said finned conduit and said S-shaped coil.

8. An absorption refrigerating system of the type including an evaporator, means for supplying refrigerant liquid to said evaporator includin an air-cooled condenser extending to substantially the level of the bottom portion of said evaporator, and means for propelling a pressure equalizing medium through the evaporator under conditions such that the pressure equalizing medium will drag or sweep liquid refrigerant upwardly through the evaporator as it travels therethrough, said system being characterized by the fact that said evaporator includes a plurality of sections at diiferent elevations and multistaged lifting conduits interconnecting evaporator sections at adjacent elevations.

9. An absorption refrigerating system of the type including an evaporator, means for supplying refrigerant liquid to said evaporator, and

means for propelling a pressure equalizing medium upwardly through the evaporator under conditions such that the pressure equalizing medium will drag or sweep liquid refrigerant through the evaporator as it travels therethrough, said system being characterized by the fact that said evaporator comprises a plurality of sections at different elevations, and a lifting conduit communicating adjacent sections lying in a plane defined by the end portions of said sections.

10. Refrigerating apparatus including an evaporator having a pair of vertically spaced sections, .agas inlet conduit connected to the lower of said sections, a gas outlet conduit connected to the higher of said sections, and a refrigerant inlet conduit connected to the lower of said sections, said evaporator including an arcuate riser conduit serially connecting said sections, said arcuate riser conduit being turned inwardly away from the plane of the outer edges of said sections and lying in the plane of the rear portions of said sections.

11. Refrigerating apparatus including an evap orator having a pair of vertically spaced sections, a gas inlet conduit connected to the lower of said sections, a gas outlet conduit connected to the higher of said sections, and a refrigerant inlet conduit connected to the lower of said sections, said evaporator including a riser conduit serially connecting said vertically spaced sections comprising a plurality of upstanding lifting portions connected by a substantially horizontal rest portion, all portions of said riser conduit being substantially coplanar.

12. Refrigerating apparatus comprising an evaporator including a plurality of vertically spaced sections, riser conduits connecting adjacent sections, one of said riser conduits including a plurality of substantially upstanding portions serially connected by a portion having no substantial inclination to the horizontal, a gas inlet conduit connected to the lowest of said sections, a liquid supply conduit connected to said lowest section, and a gas outlet connection to the highest of said sections.

13. Absorption refrigerating apparatus of the type in which an inert gas is circulated through a circuit including an evaporator in which the inert gas circulates liquid refrigerant upwardly therethrough, characterized by the fact that said evaporator includes a pair of sections vertically spaced a distance too great for elevation of liquid refrigerant therebetween in a single step by the inert gas without imposing a prohibitive circulating load on the system, and a plurality of short, serially connected rising conduits serially connecting said pair of sections.

14. In a refrigerating apparatus an evaporator of the type in which liquid refrigerant is circulated therethrough by a propelled body of an inert gas, means for supplying liquid refrigerant and inert gas to the bottom of said evaporator, said evaporator including a plurality of horizontally positioned vertically spaced coils defining freezing zones therebetween, an elevating conduit system communicating a pair of said coils comprising a short riser conduit section connected to the gas outlet portion of the lower coil of said pair of coils, a short riser conduit connected to the gas inlet portion of the higher coil of said pair of coils, and a substantially horizontal rest conduit connecting the adjacent ends of said riser conduits.

15. In a refrigerating apparatus comprising an evaporator of the type in which liquid refrigerant is circulated therethrough by a propelled body of an inert gas, means for supplying liquid refrigerant and inert gas to the bottom portion of said evaporator, said evaporator including a plurality of horizontally positioned vertically spaced coils defining freezing zones therebetween, a transfer conduit system connecting a pair of adjacent coils and lying in the plane defined by the rear coil ends comprising a horizontal conduit connected to the gas outlet portion of the lower coil of said pair, a short riser conduit connected at its lower end to said horizontal conduit, a second horizontal conduit connected to the upper end of said riser conduit, a second riser conduit connected at its lower end to said second horizontal conduit, and a third horizontal conduit connected to the upper end of said second riser conduit and to the gas inlet portion of the higher coil of said pair of coils.

MILO E. BIXLER. CURTIS C. COONS. 

